1. Field of the Invention
This invention relates to release layers and bonding materials for temporary wafer bonding processes.
2. Description of the Prior Art
Wafer bonding materials protect device features on the front side of a device substrate, and provide adhesion to a carrier substrate and mechanical support for the thinned wafers during backside processing. 3D-IC processing, especially with through-silicon via (“TSV”) and through-glass via (“TGV”) technology, requires temporary wafer bonding materials to survive processes at high temperatures and high vacuum, such as plasma-enhanced chemical vapor deposition (“PECVD”). This technology also requires that the materials can be removed easily from the wafers after processing. Additionally, lower cost of ownership is needed for the 3D-IC to be adopted by the manufacturers.
Integrated circuit and semiconductor packaging manufacturers are continually looking for temporary wafer bonding technology with low cost of ownership, that uses materials capable of surviving processing at high temperatures and under high vacuum, and that can be easily cleaned after processing. So far, no single technology/material can satisfy all these requirements. Cyclic olefin copolymer (COC) bonding materials are one class of materials that are commonly used. These COCs, such as those formulated using TOPAS® and APEL® materials, are produced by chain copolymerization of cyclic monomers with ethene. These COC materials are good for some applications, but it is very difficult to obtain a clear solution in commonly-used solvents such as d-limonene and mesitylene, and it can also be difficult to clean them off the substrates after processing.
In some temporary bonding schemes, such as ZoneBOND® zonal bonding from Brewer Science, Inc. (described in US Patent Publication No. 2009/0218560 and application Ser. No. 12/819,680, both of which are hereby incorporated by reference), carrier wafers may require pretreatment with a coating before the wafers are bonded together. Previously, a halogenated silane in a fluorinated solvent, such as 3M FC-40 Fluorinert™ electronic liquid, was used for carrier wafer preparation. However, the silane/FC-40 solution is not a practical coating material because it is unstable, and FC-40 is restricted for use in microelectronics manufacturing because of environmental concerns. Vapor deposition of fluorinated silanes has been used previously to treat the surfaces of silicon wafers. However, vapor deposition is a process that is costly because of both the time involved and the expensive, high-quality tooling it requires.
There is a need for additional bonding methods and materials that overcome the shortcomings described above.